fix(generator): delegate RSC plugin helpers for cleanup re-render + harden specs

Address review findings on PR #3590 (native RSCRspackPlugin scaffolding).

The PR added `<%= rsc_plugin_class_name %>` / `<%= rsc_plugin_import_path %>`
to the managed serverWebpackConfig.js.tt and clientWebpackConfig.js.tt
templates. Those managed templates are re-rendered during stale-config
cleanup (`rendered_template_for_cleanup`) against the restricted
`TemplateRenderContext` binding, which did not expose those helpers. For any
RSC project the cleanup render raised NameError, printed a
"could not render template ... treating as non-removable" warning, and
wrongly preserved the managed config files. Delegate both helpers in
`TemplateRenderContext` (mirroring use_pro?/use_rsc?) to fix this, and add a
regression spec asserting the RSC managed templates render (not the
TEMPLATE_RENDER_FAILED sentinel) for both webpack and rspack projects.

Also:
- Make the rscWebpackConfig.js.tt skip comment bundler-neutral so
  rspack-generated configs no longer reference RSCWebpackPlugin.
- Update two now-stale rsc_setup.rb docstrings that still described the
  RSC plugin detection/injection as webpack-only after the regex was
  broadened to match both plugin names.
- Add an rspack dedup/idempotency spec mirroring the existing webpack
  contexts, exercising the rspack branch of RSC_PLUGIN_INVOCATION_REGEX
  (verified to fail if the regex regresses to webpack-only).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: justin808

react_on_rails/lib/generators/react_on_rails/base_generator.rb

@@ -109,6 +109,14 @@ def use_rsc?
         def shakapacker_version_9_or_higher?
           generator.__send__(:shakapacker_version_9_or_higher?)
         end
+
+        def rsc_plugin_class_name
+          generator.__send__(:rsc_plugin_class_name)
+        end
+
+        def rsc_plugin_import_path
+          generator.__send__(:rsc_plugin_import_path)
+        end
       end
 
       REMOVABLE_WEBPACK_FILES = (MANAGED_WEBPACK_FILE_TEMPLATES.keys +
@@ -963,8 +971,9 @@ def rendered_template_for_cleanup(template_path)
           # current run omits those options; in that case, we preserve the directory.
           # Templates rely on config[:message] plus a small helper subset exposed by
           # TemplateRenderContext (add_documentation_reference, use_pro?, use_rsc?,
-          # shakapacker_version_9_or_higher?). Missing method delegates raise
-          # NoMethodError and are caught below, treating the file as non-removable.
+          # shakapacker_version_9_or_higher?, rsc_plugin_class_name, rsc_plugin_import_path).
+          # Missing method delegates raise NoMethodError and are caught below, treating the
+          # file as non-removable.
           # Missing config hash keys return nil silently, so any new config key
           # required by templates must be added to template_doc_config above.
           # Use TemplateRenderContext#erb_binding to avoid leaking method-local

react_on_rails/lib/generators/react_on_rails/rsc_setup.rb

@@ -306,8 +306,8 @@ def add_rsc_routes
       #
       # Updates:
       # - ServerClientOrBoth.js: RSC imports, rscConfig, RSC_BUNDLE_ONLY handling
-      # - serverWebpackConfig.js: RSCWebpackPlugin import, rscBundle param, plugin
-      # - clientWebpackConfig.js: RSCWebpackPlugin import, plugin
+      # - serverWebpackConfig.js: RSC plugin import (RSCRspackPlugin/RSCWebpackPlugin), rscBundle param, plugin
+      # - clientWebpackConfig.js: RSC plugin import (RSCRspackPlugin/RSCWebpackPlugin), plugin
       def update_webpack_configs_for_rsc
         say "📝 Updating webpack configs for RSC...", :yellow
 
@@ -489,10 +489,11 @@ def new_rsc_plugin_setup_complete?(content, is_server:)
         rsc_server_signature_in_js_code?(content)
       end
 
-      # Returns true when the file contains a real `new RSCWebpackPlugin(` invocation in actual JS
-      # code — not inside a comment or string literal. Reuses `RSC_PLUGIN_INVOCATION_REGEX` from
-      # the ClientReferences module so the routing check and the option-section partition match
-      # the same set of invocations (including whitespace/newline variants).
+      # Returns true when the file contains a real `new RSCWebpackPlugin(` / `new RSCRspackPlugin(`
+      # invocation in actual JS code — not inside a comment or string literal. Reuses
+      # `RSC_PLUGIN_INVOCATION_REGEX` from the ClientReferences module (which matches both bundler
+      # plugin names) so the routing check and the option-section partition match the same set of
+      # invocations (including whitespace/newline variants).
       def rsc_plugin_invocation_in_js_code?(content)
         content
           .to_enum(:scan, RSC_PLUGIN_INVOCATION_REGEX)

react_on_rails/lib/generators/react_on_rails/templates/rsc/base/config/webpack/rscWebpackConfig.js.tt

@@ -19,7 +19,7 @@ const extractLoader =
   });
 
 const configureRsc = () => {
-  // Pass true to skip RSCWebpackPlugin - RSC bundle doesn't need it
+  // Pass true to skip the RSC manifest plugin - RSC bundle doesn't need it
   const rscConfig = serverWebpackConfig(true);
 
   // Update the entry name to be `rsc-bundle` instead of `server-bundle`

react_on_rails/spec/react_on_rails/generators/install_generator_spec.rb

@@ -44,6 +44,39 @@ def repo_pinned_pnpm_version
     match[:version]
   end
 
+  describe "RSC managed-template cleanup rendering" do
+    # Regression: serverWebpackConfig.js.tt / clientWebpackConfig.js.tt interpolate
+    # `<%= rsc_plugin_class_name %>` / `<%= rsc_plugin_import_path %>` inside their `use_rsc?`
+    # blocks. The cleanup re-render path (rendered_template_for_cleanup) evaluates templates
+    # against the restricted TemplateRenderContext binding, so those helpers must be delegated
+    # there. If they are not, RSC managed configs render as TEMPLATE_RENDER_FAILED and are
+    # wrongly treated as non-removable (with a NameError warning printed during install).
+    render_failed_sentinel = ReactOnRails::Generators::BaseGenerator.const_get(:TEMPLATE_RENDER_FAILED)
+
+    %w[
+      base/base/config/webpack/serverWebpackConfig.js.tt
+      base/base/config/webpack/clientWebpackConfig.js.tt
+    ].each do |template_path|
+      basename = File.basename(template_path, ".tt")
+
+      it "renders #{basename} for an RSC webpack project during cleanup" do
+        rendered = render_stock_webpack_template(template_path, rsc: true, rspack: false)
+
+        expect(rendered).not_to equal(render_failed_sentinel)
+        expect(rendered).to include("RSCWebpackPlugin")
+        expect(rendered).to include("react-on-rails-rsc/WebpackPlugin")
+      end
+
+      it "renders #{basename} for an RSC rspack project during cleanup" do
+        rendered = render_stock_webpack_template(template_path, rsc: true, rspack: true)
+
+        expect(rendered).not_to equal(render_failed_sentinel)
+        expect(rendered).to include("RSCRspackPlugin")
+        expect(rendered).to include("react-on-rails-rsc/RspackPlugin")
+      end
+    end
+  end
+
   context "without args" do
     before(:all) { run_generator_test_with_args(%w[], package_json: true) }
 

react_on_rails/spec/react_on_rails/generators/rsc_generator_spec.rb

@@ -3657,6 +3657,70 @@ def index
     end
   end
 
+  # Rspack analogue of the webpack "already imports/invokes RSCWebpackPlugin" dedup contexts above.
+  # Exercises the Rspack branch of RSC_PLUGIN_INVOCATION_REGEX (/new\s+RSC(?:Webpack|Rspack)Plugin\s*\(/):
+  # if that regex regressed to webpack-only, the generator would not detect the existing
+  # `new RSCRspackPlugin(` call, would route to the add-plugin path, and inject a duplicate import —
+  # producing `Identifier 'RSCRspackPlugin' has already been declared` at build time.
+  context "when an existing rspack client config already imports and invokes RSCRspackPlugin" do
+    before(:all) do
+      prepare_destination
+      simulate_existing_rails_files(package_json: true)
+      simulate_npm_files(package_json: true)
+      simulate_existing_file("config/initializers/react_on_rails_pro.rb", <<~RUBY)
+        ReactOnRailsPro.configure do |config|
+          config.server_renderer = "NodeRenderer"
+        end
+      RUBY
+      simulate_existing_file("Procfile.dev", "rails: bin/rails s\n")
+      # Sets up the rspack shakapacker.yml so rspack_configured_in_project? is true,
+      # then overrides the client config with one that already has the native plugin.
+      simulate_rspack_pro_webpack_files
+      simulate_existing_file(
+        "config/rspack/clientWebpackConfig.js",
+        <<~JS
+          const commonWebpackConfig = require('./commonWebpackConfig');
+          const { RSCRspackPlugin } = require('react-on-rails-rsc/RspackPlugin');
+
+          const configureClient = () => {
+            const clientConfig = commonWebpackConfig();
+            delete clientConfig.entry['server-bundle'];
+
+            clientConfig.plugins.push(
+              new RSCRspackPlugin ({ isServer: false })
+            );
+
+            return clientConfig;
+          };
+
+          module.exports = configureClient;
+        JS
+      )
+
+      Dir.chdir(destination_root) do
+        run_generator(["--force"])
+      end
+    end
+
+    it "detects the existing native plugin and routes to the update path rather than duplicating the import" do
+      assert_file "config/rspack/clientWebpackConfig.js" do |content|
+        expect(content.scan(%r{require\(['"]react-on-rails-rsc/RspackPlugin['"]\)}).length).to eq(1)
+        expect(content.scan(/new\s+RSCRspackPlugin\s*\(/).length).to eq(1)
+        # The webpack plugin must never leak into an rspack config.
+        expect(content).not_to include("RSCWebpackPlugin")
+        expect(content).not_to include("react-on-rails-rsc/WebpackPlugin")
+      end
+    end
+
+    it "injects scoped clientReferences into the existing native plugin call" do
+      assert_file "config/rspack/clientWebpackConfig.js" do |content|
+        expect(content).to include("clientReferences: rscClientReferences")
+        expect(content).to include("const rscClientReferences")
+        expect(content).to include("directory: resolve(config.source_path)")
+      end
+    end
+  end
+
   # Rspack + legacy Pro variant — same as the legacy webpack exports context below,
   # but with Pro configs in config/rspack/ and rspack shakapacker.yml.
   # Verifies that the backward-compatible rscWebpackConfig.js is created in the